Glass fiber product and process



May 29, 1956 /I II E 5 /7 f/1' [Ii 11% H. M. RICHARDSON 2,748,028

GLASS FIBER PRODUCT AND PROCESS Filed July 11, 1951 r I I HENRY M.RICHARDSON,

INVENTOR.

llnited States Patent G GLASS FIBER PRODUCT AND PROCESS Henry M.Richardson, Springfield, Mass., assignor to Atlas Powder Company,Wilmington, Del., a corporation of Delaware Application July 11, 1951,Serial No. 236,137

13 (Ilaims. (Cl. 117-126) This invention relates to glass reinforcedthermoset products and more particularly to intermediate structuressuitable for the manufacture of such products.

It is an object of the invention to provide dry, resin bearing, glassfiber mats capable of being transformed directly by heat and pressureinto reinforced thermoset masses.

A further object is to provide integral structures comprising glassfibers and solid polymerizable resin composition, in adherent relationthereto, in quantity sufiicient that upon subjecting the structure tocuring temperatures under pressure, the structure is converted to ahard, dense, glass-reinforced thermoset solid.

The above and other objects will become more apparent in the course ofthe following description and in the appended claims.

The value of glass fibers as rein-forcing agent in plastics has beenamply demonstrated in recent years and fiber glass reinforced plasticshave made their appearance in diverse articles of commerce. The glassmay be in the form of fabric woven from glass yarns, which fabric, inone or several layers, is impregnated with a thermoplastic resin andallowed to set or with a thermosetting resin and cured. Moreeconomically, and with greater flexibility of operation, glass fibers incomparatively short lengths may be formed into a loosely bonded felt,the felt impregnated with the resin in liquid form, and then solidified.The felts may be formed directly over shaped molds, or in flat sheets tobe cut and laid up in molds for impregnation with the liquid resin.

By the present invention means are provided to utilize glass fibers asthe reinforcing material in plastics in a manner which eliminates theuse of liquid resins or fluid solutions of resins in the final moldingthereof. The structures of the invention contain the reinforcing fibersand solid, uncured, polymerizable resin adhering to the fibers andcementing them together to form a superficially dry, pliable mat whichmay be fitted into molds of any desired shape and cured. The quantity ofresin is sufficient that when the structure is subjected to the heat andpressure necessary for curing it fiows together around the fibers toform a continuous phase with the fibers embedded therein, and when thecure is completed the resulting products are thermoset masses shaped tothe molds and reinforced with the glass fibers of the said structures.

In the structures of the present invention the glass fibers may be anyfibers suitable for use as reinforcing fibers in plastic compositions.Particularly well suited are multifilament fibers or strands such asthose suitable for use in the manufacture of glass yarns and textiles.In the structures the fibers may be present in fabric form, having beenspun and woven; or in the form of parallel strands of long fibers; or,preferably, they may be employed in comparatively short lengths,deposited in random arrangement to form a loose felt of interlacedfibers.

The drawings show in Figure l, a structure of the invention in greatlymagnified form, being a fragment in section of the interior of such astructure. The randomly ice oriented glass fibers 11 are irregularlycoated with uncured, solid resin composition 12. At points of intersection between the fibers, as at 13, the said resin composition bindsthe fibers together whereby a coherent structure of some flexibility isformed.

Figure 2 illustrates the end product obtainable by subjecting thestructure of the invention (Figure 1) to the influence of heat andpressure. Magnification is again resorted to to make the component partsof the article visible. The resin has melted, flowed together, andbecome thermoset, this difference from the uncured resin being indicatedby designating it as 14 in the drawing. The glass fibers 11 are incloser spaced relation than in the structure of the invention, and arecompletely surrounded by and embedded in the resin phase. They serve toreinforce the solidified plastic mass, increasing greatly its flexuraland tensile strengths. 7

The polymerizable resin components of structures of the presentinvention comprise the solid pulverulent linear polyesters described inapplications Serials Nos, 92,746, now U. S. Patent No. 2,634,251;190,239, new U. S. Patent No. 2,662,069 and 190,240, now U. S. PatentNo. 2,662,070, filed May 11, 1949; October 14, 1950, and October 14,1950, respectively, all being assigned to the assignee of the presentinvention.

Such a polyester is the esterification product, with melting point of atleast C., of an ethene dicarboxylic acid with a substantiallystoichiometric quantity of a polyhydric alcohol selected from the groupsconsisting of (a) dihydric alcohols conforming to the formula wherein Ris an alkylene radical containing from 2 to 3 carbon atoms, A is a2-alkylidene radical containing from 3 to 4 carbon atoms, m and n areeach at least one, and the average sum m+n is not over 3; and (b)mixtures consisting of at least 50 mol percent of a dihydric alcoholconforming to said formula, from 0 to 50 mol percent of a memberselected from the group consisting of ethylene glycol, propylene glycol,and diethylene glycol. and from 0 to 10 mol percent of a polyhydricalcohol containing from 3 to 6 carbon atoms and at least 3 hydroxylgroups.

Polyesters of ethene dicarboxylic acids and polyols selected from thegroup hereinbefore defined in which minor proportions thereof have beenreplaced by other acids or other alcohols in order to modify theproperties of the resins in known manner are likewise suitable for usein the structures of the present invention provided the modification issufficiently minor in extent not to destroy the essentialcharacteristics of the polyesters. These characteristics includesufficient friability to permit grinding to a powder at ordinarytemperatures, and a melting point of at least 80 C., and preferablyabove C.

Polyesters which come within the scope of the above definition and whichare advantageously employed in practicing the invention include thefumarate of 2.2-di- (4 hydroxy propoxy phenyl)-propane, the maleate of2.2-di-(4 hydroxy propoXyphenyD-butane, the fumarate of a mixturecomprising 96 mol per cent of 2.2-di-(4 beta hydroxyethoxyphenyl)-propane and 4 mol per cent of glycerol, the fuinarate of amixture comprising 50 mol per cent 2.2-di-(4 hydroxypropoxyphenyl)-propane and 50 mol per cent of ethylene glycol,- themaleate of the polyoxyethylene ether of 2-butylidene diphen-ol whereinboth phenolic hydroxyls are oxyethylated and the average number ofoxyethylene groups per mol of said diphenol is 2.6, and the like. It isto be understood that in the above named polyester products theindicated acid and polyol were reacted in essentially stoichiometricproportions and the esterification carried to the extent that themelting point of the product was above 80 C. and preferably above 90 C.

Structures of resin bearing glass fibers suitable =for conversion .toglass reinforced plastic -m-ass by s bj tion to heat and pressure maycontain one .or "more -.of the above describedipolyesters as the solepolymerizable resin component. Preferably, however, the gpolymerib ableresin is a mixture ofoneormore of thesaidpolyesters-and a-nonvolatile;.polymeriz able compound adapted to serve vas a cross linkingagentrin the curing of the resin. Particularly useful .as .cross linking:agents are the .liquid-allyl esters of .polybasic acids-among which maybe named diallyl maleate, .diallylyphthalate, triallyl phosphate,diallyl succinate, and .the like. Other new volatile liquids containingpolymerizably reactive groups may likewise be employed-as thecrosslinking agent. Among such liquids are -.diallyl ,phenyl phosphonate,allyldiglycol carbonate, dicrotyl ester "of dibasieacids, "diacrylatesand dicrotonates of the lower glycols, and the like. The preferred.group of cross linking agents comprises the diallyl estersofdibasicorganic -acids,diallyl phthalate beingthe preferred mem'berofthe group.

In the polymerizable=resin componentof a structure made in accordancewith the present invention-themaximum proportion of such liquid,non-volatile cross 'linking agent to polyester is limited only by thetendencyof the uncured resin mixture to become-increasingly tacky withincreasing proportions of liquid to solidresin with a resulting decreaseinconvenience in handling the structures. The maximum amount of liquidto'be tolerated in themixtures varies with the polyester, thecrosslinking agent and the intended purposes for'which the formedstructure is to be used but, in general, amounts greater than 20% basedon the sum of polyester and cross linking agent are to be avoided, andthe preferred amount is from 5% to Operable polymerizable resincompositions :include .those containing smaller amounts of crosslinking'agent,.down to yanishingly small amounts, since theapolyestersemployed'inthe invention are themselves thermosetting.

In addition to-the fibers and polymerizable resin composition thestructures of the present invention preferably include a curing catalystfor the resin. 'Suitable catalysts include'benzoyl peroxide, lauroylperoxide, tertiary butyliperbenzoate, andother organic peroxides, andper acid esters. Inorganic catalysts such as stannic chloride, cobaltnitrate, and the like may also be-employed. The amount of catalyst inthe structure 'will vary with the activity of the catalyst, the curingtime required by .the molding process and the reactivity of theparticular resin composition in the structure. In general, however,frorn0.25- per cent to 2.5-per cent of activecatalyst ingredient basedon the resin content will be found useful in the-structures ofthe-invention. It is highly desirable that the-catalyst be welldistributed throughout the polymeriza'ble resin composition, and where aliquid cross linking agent is employed the catalyst is advantageouslydissolved therein for introduction into the'structure. If the resin isto'be composed-entirely-of solid polyester the catalyst may-be dissolvedin a-volatile liquid and sprayed onto the fibrous mat ahead-of, orsimultaneouslywith, the powdered solid-polyester. Alternatively thecatalyst may be dispersed through the powdered solid polyester by longtumbling prior to incorporation of the latter with the glass fibers.

In the structures of the invention the proportion of glass fibers topolymerizable .rcsin composition may usefully range between the limitsof fiber to 65're'sin and 65 fiber to 35 resin. Preferred structurescontain'from 45% to 55% of resin 'and from 55% to 45%-'of glass fiber.

The polymerizable'resin is presentin the structures in adherent relationto 'the glass fibers, which relation is conveniently brought about byincorporating the polyester in powder-to;granu1ar form and the liquidcross linking agent (if present) in finely dispersed droplets with theglass fibers in random orientation and subject ing the incorporatedmixture to a temperature above the melting point of the polyester butbelow the curing temperature of the resin composition for a sufficienttime to fuse the polyester particles. The fused particles absorb anyliquid cross linking agent which may be present into a substantialhomogeneous resin phase which solidifies on cooling'to'roomtemperature.T hereis some'coalcscence of resin particles but the "predominant cfiectis for the molten resin to flow over the glass fibers and collectatpoints of intersection between individual fibers to form upon cooling-astructure of sufficient mechanical strength that it can behandledwithout disintegrating or shaking out the dry resin.

In the following examples glass fiber mats bonded with insufficientmesinto be convertedto aglassreinforced plastic 'mass without the a'd'ditionof further iresin are transformed iinto dry resin-bearing tmats whichcan be so converted.

Example I Bonded glass fiber mats weighing two ounces ;.per squarefootand .madeup of multifilament glass fibers of approximately 0.00038diameter, cut into lengths of approximately 2%. inches, laid down inrandomorientation and bonded with 8% by weight of a cured coester offumaric acid with 96-mol .per cent of 2.2-di(4 beta hydroxy ethoxyphenyl)-propane and 4 mol per cent of glycerol was cut into strips 2 /2inches by 6 inches. On one face of each strip approximately 0.7 gram ofdiallyl phthalate containing dissolved therein 0.07 gram of tertiarybutyl perbenzoate was sprayed, and on'the other face 6.6 gramsofpowdered polyester resin was sprinkled. The-polyester resin was thefnmaric acid polyester of a mixed diol comprising 50 mol per cent of2.2-di('4 hydroxy propoxy phenyl)-propane and 50 mol per cent ethyleneglycol, ground to pass a 30 mesh screen. The treated strips were heatedunder infra red lamps until the resin fused. The diallyl phthalate waslargely absorbed-into the fused particles of resin and on cooling toroom tem perature, resolidification occurred, resulting ina structure of.glass fibers-to which adhered a catalyzed polymerizable mixture ofdiallylvphthalate and polyester resin, which mixture was non-tacky, andsomewhatfiexible, lending strength to the structure as awhole.

.16 plies of the resin bearing strips were laid up and compressed irramold to a height'of /2 inch and cured in a mold heated by pound steam(324 F.) for 30 minutes. In the moldedproduct the resin componentshad'flowed together to form a continuous phase, and copolymerized to aninsoluble, infusible mass heavily reinforced by the glassfibers. Thesurface was smooth and theplasticcould be shapedby machining or sawing.It exhibited very high flexural strength and very low Water absorptionon immersion for24 hours.

Example '11 Employing the same bonded glass fiber mat as was employed inExample I, and the samemanipulative technique as :described therein apolymerizable resin bearing structure was formed in which each 2.5 x6'inch ply was loaded with approximately 0.49 gram of diallyl phthalateand 4.4 grams of the fumaric acid ester-of 2.'2-di(4 hydroxy:propoxyphenyD-propane-an'd the diallyl phthalate containedin solution 0.05 gramof tertiary butyl perbenzoate. -Inthis structure the proportion of resinin'the total structure is 45% by weight.

The resin bearing fibrous structure when molded into a plastic mass ofhalf inch thickness 'had excellent'fiexural strength and very lowwater-absorption.

In the above examples 'prebonded glass fiber mats were employedfor'convenience in'handling. Thebonding'resin therein had "been cured-inthe preparation of the'mats and is not to be considered as part of thepolymerizable resin of the structures of the invention. In the followingexamples the preparation of resin bearing fiber structures from glassfibers not pre-bonded into mats is described.

Example III Six pounds of chopped strands of glass fiber averaging about2 /2 inches in length and 0.00038 inch in diameter is introducedgradually into the upper portion of a closed cylindrical chamber by abrush roll. At the base of the chamber, which is about 6 feet indiameter is a turn table rotating at about 30 R. P. M. The center of theturn table is connected through duct work to a vacuum exhaust fan, andon the turn table is placed a 3 x 4 ft. screen to collect the depositedfibers and polymerizable resins. The screen is perforated with 4; inchholes on 7 inch centers. When about 10% of the glass fibers have beenadmitted to the chamber, a solution of 10% benzoyl peroxide in diallylphenyl phosphonate issprayed into the upper part of the chamber tointermingle with the fibers, and finely ground fumarate of 2.2-di (4beta hydroxy ethoxy phenyl)-butane is also blown into the upper part ofthe chamber. The rate of addition of these polymerizable components isadjusted so that when all of the glass fibers have been introduced therewill have been added 3.4 pounds of polyester and 0.29 pound of thediallyl phenyl phosphonate solution. The screen and its mat of fiberswith particles of resin suspended therein is heated beneath infra redray lamps until the resin particles are fused, and then allowed to cool.There results a stifily flexible structure of glass fibers carryingpolymerizable resin and weighing approximately 13 ounces per square footof which approximately 65% is glass and 35% is uncured resincomposition. Such structures may be laid up in laminae or cut to desiredshapes and formed in positive molds and subjected to curing temperaturesunder pressure to yield reinforced plastic sheets or molded objects ofgreat strength and utility.

Obvious variations from the detailed instructions given in the examplesmay be practiced. Adaptation to the formation of continuous webs ofresin bearing glass fiber structure is contemplated within the purviewof the invention. If no liquid cross linking agent is to be employed orif the amount employed is insufficient to moisten the fibers and preventsifting through of the powdered resin a small proportion of volatileliquid may be sprayed along with the fibers to cause temporary adherenceof the powder, which liquid will be driven off during the fusion step.

The structures of the present invention are adapted to the production ofmany useful articles. Laid up in flat sheets and subjected to curingconditions they may be converted directly into such articles as wallpanels, table tops, shelving, and the like. Trays, suitcase halves, andsimilar shaped articles may likewise be produced from resin loaded glassfiber structures in sheet form since they are sufficiently flexible toconform to molds of simple design. More intricately shaped articles arebetter pre pared by forming the structures on screens shaped roughlylike the finished article whereby the structure is not subjected tolocalized drawing forces when pressed into a mold. Seat forms, tubs andother deep vessels, housings for electrical equipment, and the like areconveniently prepared by this technique.

What is claimed is:

1. A superficially dry, pliable mat consisting essentially of glassfibers and, in adherent relation thereto a dry solid, fusible, curableresin composition comprising a solid pulverulent polymerizable polyesterof melting point at least 80 C., and a minor proportion of a vinylpolymerization catalyst said polyester being the esterification productof an ethene dicarboxylic acid with a substantially stoichiometricquantity of a polyhydric alcohol selected 6 from the group consisting of(a) dihydric alcohols con" forming to the formula wherein R is analkylene radical containing from 2 to 3 carbon atoms, A is a2-alkylidene radical containing from 3 to 4 carbon atoms, m and n areeach at least one, and the average sum of m+n is not over 3; and (b)mixtures consisting of at least 50 mol percent of a dihydric alcoholconforming to the said formula, from 0 to 50 mol percent of a member ofthe group ethylene glycol, diethylene glycol and propylene glycol, andfrom 0 to 10 mol percent of a polyhydric alcohol containing from 3 to 6carbon atoms and at least three hydroxyl groups, the proportion of saidcurable resin composition to glass fiber being sufiicient to form, uponsubjection of the mat to heat and pressure alone, a hard, dense,glass-reinforced, thermoset solid.

2. A mat as in claim 1 wherein the said glass fibers comprise from 35%to 65% of the structure and the said resin composition comprises from65% to 35% thereof. v I I 3. A mat as in claim 2 wherein the said solidcurable resin composition contains a non-volatile cross-linking agent.

4. A mat as in claim 2 wherein the said curable resin compositioncontains from 0% to 20% by weight of a diallyl ester of a dibasicorganic acid.

5. A mat as in claim 4 wherein the said high melting polyester is thefumarate of 2.2-di-(4-hydroxy propoxy phenyl propane.

6. A mat as in claim 5 wherein the said diallyl ester is diallylphthalate and comprises about 10% by weight of the said curable resincomposition.

7. A mat as in claim 4 wherein the said high melting polyester is thefumarate of a dihydric alcohol mixture consisting of 50 mol percent2.2-di-(4-hydroxy propoxy phenyl)-propane and 50 mol percent ethyleneglycol.

8. A mat as in claim 7 wherein the said diallyl ester is diallylphthalate and comprises about 10% by weight of said curable resincomposition.

9. The process for producing a curable resin bearing structure of glassfibers which comprises the steps of forming a mat of glass fibers,incorporating therein a powdered to granular polymerizable polyester ofmelting point above C., which is the esterification product of an ethenedicarboxylic acid with a substantially stoichiometric quantity of apolyhydric alcohol selected from the group consisting of (a) dihydricalcohols conforming to the formula wherein R is an alkylene radicalcontaining from 2 to 3 carbon atoms, A is a 2-alkylidene radicalcontaining from 3 to 4 carbon atoms, m-and n are each at least one, andthe average sum of m+n is not over 3; and (b) mixtures consisting of atleast 50 mol percent of a dihydric alcohol conforming to the saidformula, from 0 to 50 mol percent of a member of the group ethyleneglycol, diethylene glycol and propylene glycol, and from 0 to 10 molpercent of a polyhydric alcohol containing from 3 to 6 carbon atoms andat least three hydroxyl groups, and a minor proportion of a vinylpolymerization catalyst, and subjecting the mat and incorporatedpolyester-catalyst mixture to a temperature above the melting point ofthe polyester and below the polymerizing temperature of the catalyzedresin for a sufficient time to fuse the polyester particles; theproportion of polyester so incorporated being suflicient to form, uponsubjection of the said structure to heat and pressure alone, a hard,dense, glass-reinforced, thermoset solid.

10. The process of claim 9 wherein the proportion of v 7 safdpo'lyestersoincorporatdliesbetween 35% and 65% of the structure by weight.

11. The process'fonproducing apolymerizable resin beai'ing structureofglass fibers-which comprises the steps of forming a mat of glassfibers'in randorn orientation, incorporatingva powdered to;granularzsolid: polymerizable polyestertofimeltingzpoint=at least 180 4C., :a..'1i.quidi'nonvolatile across linkingagent, ffln'dva minorproportionaof ia vinyl polymerization :catalyst therein,*--andsubjecting thezmat andincorporatedlingredientsto a temperature above theL'rneltingipoint of: said;po1yester and below the polymerizationtemperature 10f the mixed incorporated ingredients for 'a -sufiicienttime :to fuse the polyester particles; .the proportion of isaid cross.linking agent to said polyester; being .insuflieient V to. render thefused resin composition taeky, and the :sum of the polyester and .cross;linking -.a gent comprising from 35% to 65% by weight of thetotal-structure.

12. The process of claim 11 wherein 'the.-said;polyester is theifumarate -.of .22 -.di-r(-4-hydroxy ;pr.opoxy phenylypropane andthesaid crossim'kingagent'is dirallyl phthalate.

13. The process of claim 11 wherein the said polyester is =the fumarateof a "mixed dihy'clric "alcohol consisting of "50 'mol "percent-2'32-di-'(4'=hydrox-y*propoxy pheny1)- propane'anti O-"Inol'percente'thy-leneglycol, and the said cross linking agent is diallyl'-ph'thalate, the cross linking agent being present in amount no greaterthan 20% by weight of the sum of'said cross*linking agent and saidpolyester.

keferences' Cited' in" the. filerof this'patent UNITED "STATES PATENTS2,277,049 Reed Mar. 24, 1942 2,288,072 .Collins June30, 1942 12,505,347Brucksch .Apr. 25, 1950 2,528,235 .Loritsch Oct..31, 1950 2,543,101Francis "Feb. 27, .1951 2,550,465 Gorski Apr. .24, .1951 2,602Q037 Nelb.July 1, 1952 2,634,251 .Kass Apr. 7, 1953 {4 1,662,069 Kass r Dec. 8,1953 20 2,662;070 .=Kass .etva1. "'Dec. 8, 1953 :EORELGN PATENTS 627,255"GreatBritain Aug.'4, 1949

1. A SUPERFICIALLY DRY, PLIABLE MAT CONSISTING ESSENTIALLY OF GLASSFIBERS AND, IN ADHERENT RELATION THERETO A DRY SOLID, FUSIBLE, CURABLERESIN COMPOSITION COMPRISING A SOLID PULVERULENT POLYMERIZABLE POLYESTEROF MELTING POINT AT LEAST 80* C., AND A MINOR PROPORTION OF A VINYLPOLYMERIZATION CATALYST SAID POLYESTER BEING THE ESTERIFICATION PRODUCTOF AN ETHENE DICARBOXYLIC ACID WITH A SUBSTANTIALLY STOICHIOMETRICQUANTITY OF A POLYHYDRIC ALCOHOL SELECTED FROM THE GROUP CONSISTING OF(A) DIHYDRIC ALCOHOLS CONFORMING TO THE FORMULA